1. Field of the Invention
This invention is directed to apparatuses and methods for monitoring radiant energy delivered to a substrate. The radiant energy can be generated by a laser or flash lamp, for example. The apparatuses and methods of the invention can be used to monitor radiant energy supplied to a substrate to anneal integrated devices or circuits formed thereon, or to expose a resist layer in the performance of photolithography. The apparatuses and methods can also be used to monitor radiant energy supplied to heat a substrate to form silicide contacts coupling source/drain or gate contacts to conductive metal lines or wiring. In addition, the apparatuses and methods can be used to monitor radiant energy that triggers a chemical reaction to deposit reactant products onto a substrate, or conversely, to remove material from a substrate, for example.
2. Description of the Related Art
FIG. 1 is a general diagram of a previous device 1 for monitoring the amount of energy delivered to a substrate 2. The device 1 generally includes a laser 3 generating radiant energy 4, a beam splitter 5, optical element(s) 6, a stage 7, and an energy detector 8. The radiant energy 4, i.e., laser light, is supplied to the beam splitter which reflects a portion of the incident radiant energy 4' to the optical element(s). The optical element(s) includes one or more mirrors or lenses which modify the radiant energy 4' in some predetermined fashion. For example, the optical element(s) can be used to focus the radiant energy 4' onto the substrate, or to magnify or reduce the radiant energy's image field. The optical element(s) directs the light to the substrate which is positioned on the stage. A portion of the radiant energy 4" generated by the laser is transmitted through the beam splitter and impinges on the energy detector. The device 1 monitors the amount of radiant energy 4' supplied to the substrate by determining the amount of radiant energy 4" received by the energy detector.
The proper functioning of the device 1 depends upon the assumption that the radiant energy 4" tapped upstream along the optical path from the optical element(s), is related in a fixed manner to the amount of radiant energy 4' supplied to the substrate downstream along the optical path from the optical element(s). Although the amount of radiant energy 4" received by the energy detector may be related to the radiant energy 4' delivered to the substrate upon calibration of the device 1 and shortly thereafter, such relationship generally changes with time due to thermal or mechanical drifts of the optical element(s) or changes in the performance thereof. As a result, the actual amount of radiant energy 4' delivered to the substrate may be significantly different than expected, leading to over- or under-treatment of the substrate with the radiant energy 4' and consequent failure of the radiant-energy processing of the substrate. It would be desirable to overcome this disadvantage of previous devices and techniques used to monitor the radiant energy supplied to a substrate.